Hourly benzene readings as high as 191.3 ug/m3 were detected at noon on April 25, by a real-time air monitor on the First Nation’s northern border. Wind direction indicated the high levels appeared to be connected to a plant shutdown underway at INEOS Styrolution, a chemical manufacturer. Ontario’s environment ministry has set the annual average limit for the cancer-causing substance at 0.45. The province has not set an hourly limit.